[Unclenick]

It took a lot of ingenuity. The Garand bolt and receiver, for example, have helical lug mating surfaces with a 0.2 inch pitch at a 1.16 inch pitch diameter that has to be radially square within half a thousandth. That's easy to put on the bolt lugs with a lathe and toolpost grinder. But the receiver is a tougher nut to crack. When bidders first looked at Garand's receiver drawings a number of them said there was no way to make it. Garand then went about proving them wrong by designing the jigs and fixtures that made it all possible to do.

I think you'll find every design had somewhat unique methods of approaching the problem based on when and where the work was being done.